The use of Ultra Dense Networks (UDNs) is anticipated to be one of the 5G architectural solutions for providing high speed services with high quality of service (QoS) and quality of experience (QoE) in highly populated areas. In a UDN, a plurality of small cells or microcells may be deployed within the coverage area of a large cell or macrocell. Because the coverage of a microcell is limited compared with that of a macrocell, it is possible for a user equipment (UE) to move from one microcell to another very frequently, which may increase the number of microcells with which the UE needs to have a security trust relationship.